// Prevent select2 from flipping the dropdown upward
// https://stackoverflow.com/a/47912914/2523254
// needed for mobile


(function($) {
  
	var Defaults = $.fn.select2.amd.require('select2/defaults');
  
  $.extend(Defaults.defaults, {
  	dropdownPosition: 'auto'
  });
  
 	var AttachBody = $.fn.select2.amd.require('select2/dropdown/attachBody');
  
  var _positionDropdown = AttachBody.prototype._positionDropdown;
  
  AttachBody.prototype._positionDropdown = function() {
   
    var $window = $(window);
   
		var isCurrentlyAbove = this.$dropdown.hasClass('select2-dropdown--above');
		var isCurrentlyBelow = this.$dropdown.hasClass('select2-dropdown--below');
   
		var newDirection = null;
   
		var offset = this.$container.offset();
   
		offset.bottom = offset.top + this.$container.outerHeight(false);
		
		var container = {
    		height: this.$container.outerHeight(false)
		};
    
    container.top = offset.top;
    container.bottom = offset.top + container.height;

    var dropdown = {
      height: this.$dropdown.outerHeight(false)
    };

    var viewport = {
      top: $window.scrollTop(),
      bottom: $window.scrollTop() + $window.height()
    };

    var enoughRoomAbove = viewport.top < (offset.top - dropdown.height);
    var enoughRoomBelow = viewport.bottom > (offset.bottom + dropdown.height);
    
    var css = {
      left: offset.left,
      top: container.bottom
    };

    // Determine what the parent element is to use for calciulating the offset
    var $offsetParent = this.$dropdownParent;

    // For statically positoned elements, we need to get the element
    // that is determining the offset
    if ($offsetParent.css('position') === 'static') {
      $offsetParent = $offsetParent.offsetParent();
    }

    var parentOffset = $offsetParent.offset();

    css.top -= parentOffset.top
    css.left -= parentOffset.left;
    
    var dropdownPositionOption = this.options.get('dropdownPosition');
    
		if (dropdownPositionOption === 'above' || dropdownPositionOption === 'below') {
    
    		newDirection = dropdownPositionOption;
    
    } else {
    		
        if (!isCurrentlyAbove && !isCurrentlyBelow) {
      			newDirection = 'below';
    		}

    		if (!enoughRoomBelow && enoughRoomAbove && !isCurrentlyAbove) {
      		newDirection = 'above';
    		} else if (!enoughRoomAbove && enoughRoomBelow && isCurrentlyAbove) {
      		newDirection = 'below';
    		}
    
    }

    if (newDirection == 'above' ||
        (isCurrentlyAbove && newDirection !== 'below')) {
      css.top = container.top - parentOffset.top - dropdown.height;
    }

    if (newDirection != null) {
      this.$dropdown
        .removeClass('select2-dropdown--below select2-dropdown--above')
        .addClass('select2-dropdown--' + newDirection);
      this.$container
        .removeClass('select2-container--below select2-container--above')
        .addClass('select2-container--' + newDirection);
    }

    this.$dropdownContainer.css(css);
   
  };
  
})(window.jQuery);